2,3-Diaminopyridinium 2-hydroxybenzoate

In the title molecular salt, C5H8N3 +·C7H5O3 −, the 2,3-diaminopyridinium cation is essentially planar, with a maximum deviation of 0.006 (2) Å. In the crystal, adjacent cations and anions are linked by pairs of N—H⋯O hydrogen bonds, generating R 2 2(8) loops. These dimers are linked by further N—H⋯O hydrogen bonds and C—H⋯O interactions to form sheets lying parallel to (001). A typical intramolecular O—H⋯O hydrogen bond is also observed in the salicylate (2-hydroxybenzoate) anion, which generates an S(6) ring. The crystal structure also features π–π stacking interactions between the pyridinium rings of the cations, with a centroid–centroid distance of 3.5896 (15) Å.

In the title molecular salt, C 5 H 8 N 3 + ÁC 7 H 5 O 3 À , the 2,3diaminopyridinium cation is essentially planar, with a maximum deviation of 0.006 (2) Å . In the crystal, adjacent cations and anions are linked by pairs of N-HÁ Á ÁO hydrogen bonds, generating R 2 2 (8) loops. These dimers are linked by further N-HÁ Á ÁO hydrogen bonds and C-HÁ Á ÁO interactions to form sheets lying parallel to (001). A typical intramolecular O-HÁ Á ÁO hydrogen bond is also observed in the salicylate (2-hydroxybenzoate) anion, which generates an S(6) ring. The crystal structure also featuresstacking interactions between the pyridinium rings of the cations, with a centroid-centroid distance of 3.5896 (15) Å .

Experimental
Hot methanol solutions (20 ml) of 2,3-diaminopyridine (27 mg, Aldrich) and salicylic acid ( 34 mg, Merck) were mixed and warmed over a heating magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature.
Brown plates of the title compound appeared from the mother liquor after a few days.

Refinement
All hydrogen atoms were located from a difference Fourier maps and refined freely [N-H = 0.88 (2)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.  (7) 0.0366 (9) −0.0028 (6) 0.0031 (7) 0.0032 (7) Geometric parameters (Å, °)